The present invention relates to IC test equipment of the type wherein IC elements are brought in a horizontal plane to a predetermined position for testing them.
IC elements are classified into various types according to their terminal lead-off configuration. Of them, an IC element of the type having its terminals led out from four sides of a plastic molding is difficult to slide directly on a guide rail. Conventionally, an X-Y transport mechanism is used by which chucks having sucked thereto such IC elements are carried in the X-Y direction, i.e. in the horizontal direction and are mounted on sockets provided on a performance board of a test head. The X-Y transport mechanism includes X-axis guide rails, a Y-axis guide rail movable on the X-axis guide rails in the X-axis direction, and a carrier head movable on the Y-axis guide rail in the Y-axis direction. The carrier head has vertical drivers each of which is driven by an air cylinder, for example, and air chucks affixed to the vertical drivers and driven in the vertical direction and suck up thereto and hold IC elements.
FIG. 1 shows the construction of each of the socket and the air chuck for use in the conventional IC test equipment. Reference numeral 10 indicates an IC element to be tested. The IC element 10 has its terminals 11 led out from four sides of a plastic molding as referred to above. The terminals 11 are held by terminal holders 21 of an insulating material, protrusively provided on an air chuck 20, and are urged into contact with spring contacts 31 of a socket 30. The socket 30 is packaged on a performance board PB. The performance board PB, the socket 30 and a circuit provided on the underside of the performance board PB constitute a test head.
The air chuck 20 has a centrally-disposed air suction hole 22 and sucks in air through the air suction hole 22 to suck up the IC element 10. The air chuck 20 is equipped with a heater 23 so that the IC element 10 can be tested under a thermally stressed condition. The air chuck 20 is heated by the heater 23 to maintain the temperature of the IC element 10 under test. This embodiment is shown to employ a hot plate, as means for preheating the IC element 10, to prevent that the throughput of testing all IC elements decreases due to the time required for heating each of them up to a predetermined temperature in advance to each test. That is to say, a plurality of IC elements to be tested are placed on the hot plate (not shown) heated at a predetermined temperature so that they are subjected to a predetermined thermal stress. The IC elements 10 thus preheated are each sucked up by the air chuck 20 and carried to the socket 30. For such a reason, the air chuck 20 is also provided with the heater 23 for holding the temperature of the chuck 20 close to the temperature of the preheated IC element 10 to prevent the temperature of the latter from dropping during transportation.
While the IC element 10 sucked by the air chuck 20 is being carried toward the socket, the heater 23 keeps the temperature of the IC element 10 unchanged. On the other hand, the socket 30 is held at room temperature, and consequently, when the IC element 10 is attached to the socket 30, the heat stored in the former escapes through the terminals 31 of the latter, resulting in the lowered temperature of the IC element 10. On this account, the prior art is defective in that IC elements are not always tested at predetermined temperatures.